Abstract: Sediment transport is a key scientific concern in water engineering and in the management of soil and water resources in the Yangtze River Basin. Using observed sediment discharge data from 13 hydrological stations located along the mainstream and major tributaries, together with precipitation records from 175 meteorological stations during 1960—2024, this study analyzed the spatiotemporal variation in sediment load and its main influencing factors. The Mann-Kendall test, sequential clustering analysis, and double mass curve method were applied. The results indicate a significant downward trend in annual sediment load along the Yangtze River mainstream (P < 0.01). A major abrupt change occurred at Xiangjiaba Station in 2010, while abrupt changes at the other stations were identified in 2001. After these transition points, sediment load declined by 67.76%—90.04%. Since 2001, the sediment yield modulus of the eight major tributaries has also decreased markedly, with reductions of more than 80% in the Hanjiang and Yuanjiang rivers. These changes have substantially reshaped the erosion–deposition pattern along the mainstream. The Cuntan—Yichang reach changed from an erosional state to a depositional state, whereas the Yichang—Hankou reach changed from deposition to erosion. Precipitation accounted for approximately 5% of the potential increase in sediment load; however, this influence was largely counteracted by intensive human activities. Overall, sediment retention by cascade reservoir systems and the implementation of soil and water conservation measures were the dominant factors leading to the sharp reduction in sediment load in the Yangtze River mainstream and its tributaries.